It is known that isocyanate-based formulations are useful laminating adhesives for flexible packaging. The solventless formulations, which consist of a polyol (part A) and an NCO-terminated polyurethane prepolymer (part B), are meter-mixed immediately before the laminating process and used to adhere superposed layers of one or more materials. For example, European Patent Application # 93114668.2 discloses such formulations wherein the part A and part B components are meter-mixed at temperatures between 20° C. and 50° C.
A drawback in this prior art reference is the formulation's initial viscosity. The formulations, which have initial viscosities greater than 25,000 mPa·s at 25° C.+/−5.0° C., are difficult to process.
Therefore, there remains a need for solventless isocyanate-based laminating adhesives having enhanced processing characteristics at reduced temperatures.